1. field of the Invention
This invention relates to an orthodontic appliance, and more particularly to a metal bracket for receiving a wire which transmits orthodontic force to the tooth to which the bracket adheres.
2. Prior Art
In general a metal bracket of the type above referred to comprises a bracket body for receiving and securing the wire and a support base for supporting the body, said support base being bonded to the tooth with an adhesive. Hithertofore, the base has been modified in various ways to give strong adhesion between the base and the tooth.
A metal bracket of one conventional type comprises a support base having a plurality of through-pores, each spaced at constant intervals along the periphery of the base. A metal bracket similar to this type comprises a support base having a plurality of through-pores not only at its periphery but also within its whole region. In either case an adhesive applied to the back side of the base partly comes out through the through-pores at the periphery of the base and solidifies on its surface, thereby providing strong adhesion in addition to the bonding between the back side of the base and the tooth. This type of the bracket, however, has a disadvantage that when brushing the tooth the adhesive on the surface of the support base is gradually abrased and finally worn out so that the metal bracket is detached off the tooth.
As another known type of the metal bracket, instead of the support base of metal plate a net made of metal is secured to a bracket body. However, it happens that the net often gets unknitted in its circumference and consequently the adhesion between the net and the tooth becomes lower. As a modified type, the metal net is provided under the thin metal plate support base. It, however, costs high since additional process is required for the production. Furthermore, the modified bracket becomes thick in its height so that it is not comfortable for patients.